Apparatus for casting cylindrical rolls



Sept. 26, 1939. J, s ZAHN 2,173,955

APPARATUS FOR CASTING CYLINDRICAL ROLLS Filed Feb. 28, 1938 I f ,EMC/moj ldd/w55.' u @/UMQ. Zeb/n) www www5' Patented Sept. 26, 1939 2,173,955APPARATUS FORl CASTING CYLINDRICAL ROLLS JohnfS. Zahn, Lima, Ohio,assgnor to The Ohio Steel Foundry Company, Lima, Ohio, a corporation ofOhio Application February 28, 1938, Serial No. 193,008

4 Claims.

This invention relates to improvements in methods and apparatus Aforproducing hollow' rolling mill rolls and similar tubular metal castings.Among the objects of the invention is to provide a simple and economicalmethod and apparatus in connection with the usual foundry moldingprocesses to extend an auxiliary heat conducting medium such as a pipethrough the hollow cylin- ,drical mass so as to aid in cooling theinterior l0 surface of the casting while in the mold.

It has been generally recognized that hollow mill rolls have certainadvantages over said rolls, particularly as to more uniform grainstructure and responsiveness to heat treatment in smallersectionedmasses, giving them greater resistance to breakage and failure than withsolid castings, in which excessive internal stresses are more likely tobe set up. One of the principal diiiculties in the production of suchhollow rolls, however, has been that of introducing'in the moldsatisfactory means for equalizing the temperature of the interior andexterior surfaces of the hollow casting while it is cooling in the mold.

This problem can be better understood when it `is explained that incasting such heavy rolling mill rolls, it is customary to stand them onend and provide what is known as a swirl gate near the bottom so thatthe metal enters the mold tangentially to the bottom cylindrical portionof the mold. The hot metal thus enters the mold with a spiral motionabout the axial core. It has been proposed to introduce a cooling mediumsuch as a pipe for air, steam, water or the like, through the centercore, made of usual core sand, but this has been-found unsatisfactorybecause the swirling motion of the metal soon erodes the sand, and themetal reaches the pipe in places making it difficult to remove the pipe,and also causing some of the core sand to be burned into the casting.Attempts to dispense with a core sand covering have only increased thediiculty of removing the pipe to a point where it often has had to bemachined out of the casting after the latter has been removed from themold.

In carrying out my invention, I utilize a plurality of annular bakedclay sections of high refractory value, which are arranged end-to-end toform a continuous sleeve over the central pipe, and thus provide a corecapable of resisting erosion of the metal and yet which is relativelyeasy to remove. The invention may best be understood by reference to theaccompanying drawing, in which Fig. 1 illustrates the application of myimproved process and apparatus to a molding ask and shows the ilask andhollow roll in longitudinal section, but with the core and center pipeshown in part elevation.

Fig. 2 is an enlarged detail section taken on line 2-2 of Fig. 1. 5 Fig.3 is an enlarged detail longitudinal section showing the arrangement ofthe pipe and center core construction.

Referring to details of the apparatus illustrated in the drawing, a askI0 of the usual form 10 is shown with a cylindrical mold or impressionII therein formed in molding sand in the usual manner. ,A gate of theusual swirl type, not shown, may be connected to the lower end of theimpression, but need not be described in detail as 15 it forms no partof the present invention.

In place of the usual center core made of baked sand, I provide acomposite core structure, herein consisting of a length of hollow metalpipe I5, and surrounded by a hollow tile covering, 20 consisting of aplurality of baked clay sleeve sections IB, IE arranged in end-to-endrelation along said pipe, as shown in Fig. 1. Each of the clay sleevesections I6 is preferably interlocked with l adjacent sections, as by atongue I'I fitting into 25 annular grooves I8 formed in the abuttingends of said sleeves, as is best shown in Fig. 3. The clay sleevesections IB are preferably mounted 0n the pipe with a loose fit so as toleave a space therebetween, as indicated at I9 in Fig. 3.

Said sleeves are preferably made of baked clay, having a relatively highrefractory value similar to the material used in tiles employed inpouring ladles and other refractory furnace structures. I have foundthat such baked clay sleeves have 35 ample strength to withstandconsiderable pressures at high temperatures, and yet have sutilcientplasticity to withstand erosion of the hot metal as it is introduced inthe mold.

Means are also provided for holding the sleeves 40 together underyielding pressure, and yet permit expansion during the moldingoperation, In the form shown herein, the lower end of the pipe I5 hasnuts 20 and 2l mounted thereon, and adjustable on opposite sides of thebottom wall IIIa of 45 the iiask. When tightened against said wall saidnuts provide an anchor for one end of the pipe relative to said flask. Awasher 22, preferably recessed at I'Ia to receive the tongue I1 of theadjacent clay section, is seated above the inner ad- 50 justing nut 2|,and the lowermost clay sleeve I6 abuts against said washer, as shown inFig. 1. The uppermost clay sleeve I 6 projects through the upper end ofthe iiask, but is supported in lateral engagement with the topmwallthereof.

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A washer 23 engages the outer end of the uppermost clay sleeve, and isurged downwardly thereagainst by coil spring 24 which has its upper endengaged with an adjustable nut 25 threaded on the pipe l5. The coolingmedium such as water, air or steam, can be supplied for circulationthrough the pipe by any suitable connections such as the T-members 26and 21 at the bottom and top of the ilask as shown in Fig. 1.

With the construction and arrangement above described, the severalsleeve sections are maintained under suicient yielding pressurelongitudinally of the core to keep them in snug engagement with eachother, but permitting longitudinal expansion orcontraction of the coreduring the molding process. It will be understood that in filling themold with molten steel, the core is progressively heated from the bottomof the mold toward the top. By building up Vthe core of individualsleeve sections as herein disclosed, each section is permitted to expandindependently of the others and thus accommodates itsef to rapid changesin temperature without transmitting the resulting stresses to'adjacentparts of the core. As a result the core structure is capable ofwithstanding the thermal shocks imposed thereon during the moldingprocess, and it expands or `contracts longitudinally under yieldingcompression of the spring 24 as required by changing temperatureconditions.

While the mold is being lled, the cooling medium can be passed throughthe pipe as required to reduce the temperature of the interior of thecasting, as is desirable with hollow castings of this character. Theclay sections are readily removable, usually being comparatively brittleafter cooling to atmospheric temperatures so that they are easily brokenup. Due to the clearance or space maintained between the outside of thepipe and the inside of the sleeves during the pouring and coolingoperations, the pipe is also quite loose within the sleeves, andtherefore readily removable from the casting after the latter has beencooled and is taken from the mold.

While the preferred embodiment illustrated in the drawing has a hollowpipe for conducting a cooling medium such as Water, air, steam or thelike, through the hollow roll, it will be understood that under someconditions the pipe may be replaced by a solid metal bar passing throughthe hollow clay tile core, and the thermal capacity of said metal barcan be utilized to carry oi the heat by conduction from the interior ofthe mold.

Although I have shown and described certain embodiments of my invention,it will be understood that I do not wish to be limited to the exactconstruction shown and described, but that various changes andmodifications may be made Without departing from the spirit and scope ofmy invention as defined in the appended claims.

I claim as my invention:

1. In an apparatus for casting hollow steel rolls and in combinationwith a mold body, a central core structure therefor consisting of a pipeextending through the mold body and projecting at the end thereof todissipate heat from the casting,

and a sleeve made of refractory tile surrounding said pipe inindependent self-supporting relation therewith to provide sufficientclearance to permit endwise removal of said pipe independently of saidsleeve after the casting is formed.

2. In an apparatus for casting hollow steel rolls and in combinationwith a mold body, a central core structure therefor consisting of a pipeextending through the mold body having connections for passing a coolingmedium therethrough, and a baked clay sleeve tting loosely around saidpipe and having suflicient strength and heat resistance to withstand thepouring temperature of steel and permit endwise removal of said pipefrom within said sleeve after the casting is formed.

3. In an apparatus for casting hollow steel rolls and in combinationwith a mold body, a central core structure therefor consisting of a pipeextending through the mold body having connections for passing a coolingmedium therethrough, and a plurality of baked clay sleeve sec tionsdisposed in abutting relation to each other and forming aself-supporting sleeve surrounding said pipe to permit endwise removalof the latter from said sleeve after the casting is formed.

4. In an apparatus for casting hollow steel rolls and in combinationwith a mold body, a central core structure therefor consisting of ametallic cooling member extending through the mold body and projectingat opposite ends thereof, a baked clay sleeve fitting loosely aroundsaid cooling member, means adjacent one end of said mold body forming anabutment for one end of said clay sleeve, and yielding means adjacentthe end of said cooling member beyond the opposite end of said moldlbody for holding said sleeve against said abutment, but permittinglongitudinal I expansion of said sleeve relative to said cooling member.

JOHN S. ZAHN.

